insulation resistance with a Fluke 1652

[BAZ]

Hello, i have just bought a Fluke 1652 and was testing lighting circuits, i bridged out the phase and nautral and tested between the phase and earth with 500 volts, the results that keep coming up is less than 500 M ohms is this right or am i doing something wrong. What would your results normal be.

thanks

baz

 

[danzor]

>2000

 

[EasyFox]

What reading are you getting.

The minimum is 0.5 Megohm
But anything less than 2 Megohm needs further investigation due to possible faults.

So I'd want to be seeing above 2 Megohm (>2)
You'll rarely get 500 Megohm (>500) unless a new installation.

 

[Shakey]

like the lads said, what are you getting?

i always get my students to measure a circuit with about 50Mohms on it, we use meggers, and they get so used to seeing >299Mohms, that the first time they get something else they think the sky has fallen in on them, even tough they are 100 times greater than the minimum reading!

 

[BAZ]

im getting >500 megoham, my test voltage is 500 volts, i might be doing the test wrong, i link the phase and nautral in the distribution board and then test between the phase and earth bar in the distribution board, im not getting any other reading >500 megohm. It is a new installation, there all lighting circuits wired is 1.5 pvc in conduits.

thanks

Baz

 

[EasyFox]

On the Fluke you will not get any better than >500 meg.

You are doing it right testing at 500volt (so long as not elv circuit) but if it was a new installation you will need to test between
line - neutral
line - cpc
neutral - cpc
after removing lamps / dimmers / neons / trannys etc

For PIR's it is acceptable to link neutral & line then test to cpc, lazy but acceptable

 

[BAZ]

Thanks Easyfox, i just got the fluke and was worried i was doing some thing and i need to fill out some test sheets.

 

[jibspark]

like the lads said, what are you getting?

i always get my students to measure a circuit with about 50Mohms on it, we use meggers, and they get so used to seeing >299Mohms, that the first time they get something else they think the sky has fallen in on them, even tough they are 100 times greater than the minimum reading!

LOL that happened to me at college! all my work is new circuits, so at college when it came up at a reading <200MOhms i didn't have a clue why! i just couldn't get my head around the fact that ANY reading less than infinity would be acceptable!

 

[EasyFox]

Just saw this again & remembered that on Thursday (yesterday) this happened to me.
At 16:00 on my way home I take a call on the mobile from a bathroom fitter asking if I'd mind dropping by to give him a hand, as he was getting funny results (as in a fail 0.33Meg) on a ringmain doing IR test "I'll pay you for your time, cant work it out all I've done is extend the ring to power a shower"

Why did he call me, because I changed the cu a month ago & left one of my contact labels on the cu. I had no problems with any of the circuits when I tested it.

Anyway turned up as it was on my way home, found him upstairs poking 500v round the ring showing me the 0.33meg result " there see, are you sure you tested it because i've checked your cert & you got >200Meg"

So pointed out that in my oppinion it was a neon some where, told him to do a walkround & unplug the trailing lead with neon & retest..................... >200Meg yeeeeha
(it feels sooooooooo good when your right dont it)

His response " well thats the sort of thing that they should teach on the part P course, I didnt know what to do as its the first failed IR reading I've had"
I felt sorry for him he was at the crying stage when he called me, so told him to call if unsure in the future............that I may live to regret but heyho goodwill to all.

 

[DonaldJ]

cant work it out all I've done is extend the ring to power a shower

Surely not!

 

[linzilou72]

See this is what I am saying why can't the electrics just lbe left to us sparks, as soon as they get a result thats not perfect the kitchen fitters and plumbers don't understand the electrical theory to find out what's wrong.
I am wondering if they even understand what the results mean??

I have a friend who's a decorator and used to put work my way. He was always joking about how much I was earning and I think got a little bit jealous, even though I explained the cost of materials, testing meters etc He then bragged one day that he was going to do a Part P and could be registered in 4 weeks. Well I found that quite scary especially as I had seen him with his favourite friend charlie on a regular basis.

Now this may have been a load of ol bull but what if it isn't????? As there are a lot of courses advertised for non-electricians how do you learn theory in that space of time???

 

[PAUL M]

I dont think they bother learning em impedance triangles and phasors in such a short space of time do they its just the basics i think you will find,i remember doing my electrical principles when i did the old 236 it was a nightmare ,no multi guess exams then ,you either nuckled down and passed it or it was the dreaded resit. Maybe when a few of these jokers have done themselves some serious harm these courses might get stopped.

 

[Shakey]

I dont think they bother learning em impedance triangles and phasors in such a short space of time do they its just the basics i think you will find,i remember doing my electrical principles when i did the old 236 it was a nightmare ,no multi guess exams then ,you either nuckled down and passed it or it was the dreaded resit. Maybe when a few of these jokers have done themselves some serious harm these courses might get stopped.

why does a domestic installer need to know about impedence triangles????

Just saw this again & remembered that on Thursday (yesterday) this happened to me.
At 16:00 on my way home I take a call on the mobile from a bathroom fitter asking if I'd mind dropping by to give him a hand, as he was getting funny results (as in a fail 0.33Meg) on a ringmain doing IR test "I'll pay you for your time, cant work it out all I've done is extend the ring to power a shower"

Why did he call me, because I changed the cu a month ago & left one of my contact labels on the cu. I had no problems with any of the circuits when I tested it.

Anyway turned up as it was on my way home, found him upstairs poking 500v round the ring showing me the 0.33meg result " there see, are you sure you tested it because i've checked your cert & you got >200Meg"

So pointed out that in my oppinion it was a neon some where, told him to do a walkround & unplug the trailing lead with neon & retest..................... >200Meg yeeeeha
(it feels sooooooooo good when your right dont it)

His response " well thats the sort of thing that they should teach on the part P course, I didnt know what to do as its the first failed IR reading I've had"
I felt sorry for him he was at the crying stage when he called me, so told him to call if unsure in the future............that I may live to regret but heyho goodwill to all.

Easyfox,

I guess it just proves theres Part P courses and Part P courses

When I designed the installation boards for my EAL DEI courses I delibertely purchased cooker control units and shower isolators with inbuilt neons. If they forget to isolate they get 0.25Mohm, and they all learn from it

Like I said, you have to see a bad reading to appreciate a good one

 

[PAUL M]

why does a domestic installer need to know about impedence triangles,

they dont,linzilu was enquiring how someone could learn electrical principles in a couple of days so i used it as an example of the kind of long winded bumph they dont need to learn.did your students ever get their results following your computer virus.

 

[Moog]

Aren't there three levels of Part P (a b c) and you do have to have the electrical theory for the advanced one?